Process for the selective hydrogenation of hydrocarbon mixtures



United States Patent 3,471,400 PROCESS FOR THE SELECTIVE HYDROGENATION 0F HYDROCARBON MIXTURES Jean Cosyns, Nanterre, Hauts-de-Seine, and Jean-Frangois Le Page, Rueii-Malmaison, Hauts-de-Seine, France, assignors to Institut Francais du Petrole des Carhurants et Lubrifiants, Rueil-Malmaison, Hauts-de-Seine, France N0 Drawing. Filed Sept. 19, 1966, Ser. No. 580,193 Claims priority, application France, Sept. 23, 1965,

Int. or. dra 23/02 U.S. Cl. 208-255 11 Claims ABSTRACT OF THE DISCLOSURE The present invention relates generally to a process for selectively hydrogenating a mixture of hydrocarbons, and particularly to hydrogenating liquid mixtures of hydrocarbons in the presence of a catalyst containing metallic nickel and/or metallic cobalt.

The prior art methods of hydrogenating hydrocarbons and the catalysts useful therein are set forth in Chemistry of Petroleum Hydrocarbons, vol. 3, Reinhold Publishing Corp., New York (1955), particularly Chapter 51 entitled, Catalytic Hydrogenation of Hydrocarbons, pp. 283-325, and Chapter 52 entitled Hydrogenation of Cracked Oils, Catalytic Naphtha, Catalytic Cycle Stock and Shale Oil, pp. 327-339. The prior art is further disclosed in Catalysis, vol. 3, Reinhold Publishing Corp., New York (1955), particularly Chapter 3 entitled Catalytic Hydrogenation of Olefinic Hydrocarbons, pp. 79-108.

In vol. 3 of Catalysis the subject of selective hydrogenation is treated on pages 8l89 and 103 with particular references to the selective hydrogenation of olefins in cracked naphtha to produce motor fuel with high octane number on page 83, and the deliberate poisoning of catalysts for selective hydrogenation on page 103. The preparation and activity of nickel, cobalt and nickel-alumina catalysts is particularly set forth on pages 98, 101 and 104, of vol. 3 of Catalysis.

It is an object of the present invention to improve the selectivity in the process of hydrogenating hydrocarbon mixtures.

Other objects of the present invention are stable petroleum fractions having improved commercial value.

Still other objects of the invention are improved nickel and/or cobalt selective catalysts.

Another object of the present invention is an improved selective catalyst resulting from deliberate poisoning.

A particular object of the present invention is the improved mixed hydrocarbon hydrogenation process having a. selective catalyst obtained by carbon monoxide poisonmg.

Upon further study of the specification and claims, other objects and advantages of the present invention will become apparent.

In the present invention, a normally liquid mixture of hydrocarbons, particularly including gum-producing hy- 3,471,400 Patented Oct. 7, 1969 ice drocarbons and having less than 50 parts per million by weight of sulfur is selectively hydrogenated by contact with hydrogen at a temperature between about 50 and 250 C. in the presence of a catalyst containing metallic nickel and/or metallic cobalt and carbon monoxide, wherein the carbon monoxide is added in the ratio of 10 to 1000 parts per million parts by volume of the hydrogen.

By gum-producing hydrocarbons are meant diolefinic and/or alkenyl-aromatic hydrocarbons. These hydrocarbons have a boiling point range between about 20 and 220 C. under 76 cm. of mercury and are present in particular refinery fractions, such as the products of pyrolysis, cracking, steam cracking and dehydrogenation, and generally are present in a concentration of 1 to 40 volume percent.

Particular examples of the diolefinic hydrocarbons have 5 to 14 carbon atoms, such as isoprene, piperylene, 2,4-heptadiene, 1,3-decadiene, phenyl-2-butadiene-1,3, cyclohexadiene and cyclopentadiene.

The examples of the alkenyl-aromatic hydrocarbons have 8 to 12 carbon atoms, such as styrene, a-methylstyrene and 2butenylbenzene.

In the selective hydrogenation of the present invention, the diolefinic and/or alkenyl-aromatie hydrocarbons are converted into monoolefinic and/ or alkylaromatic hydrocarbons without appreciable hydrogenation of the monoolefinic, aromatic or alkyl-aromatic unsaturated hydrocarbons already present.

Stable fractions, as indicated by a good period of induction, are produced without lowering the commercial value as measured by the octane number. A good period of induction is defined in the present invention as being at least 360 minutes.

To accomplish the selective hydrogenation contemplated by the present invention, metallic nickel or metallic cobalt cannot be used alone because of their low selectivity. It is known in the prior art, however, to improve the selectivity of catalysts by the addition of sulfur compounds. These sulfur compounds can be added to the charge or to the hydrogenating gas, or else can be present naturally in the gas or in the charge, as for example, in certain fractions produced during the cracking process.

However, when the charge does not contain any sulfur compounds or only small proportions, for example, in amounts less than 50 p.p.m., and especially less than 30 ppm. by weight, it is generally not desirable to add sulfur compounds because such an addition, besides being troublesome, can be detrimental to the quality of the final products.

Because of the detrimental effect of the sulfur compounds, some or all of the fraction, after having been subjected to a first hydrogenation stage for the elimination of the diolefines and/or the alkenyl-arornatics, is delivered to a second hydro-desulfurization and hydrogenation stage which decomposes the sulfide and hydrogenates the olefins in such a manner as to produce a suitable charge for the extraction of aromatic hydrocarbons.

Little interest has therefore been shown in adding sulfur compounds prior to the first stage since they would have to be thoroughly eliminated thereafter to produce aromatic fractions which, to satisfy the requirements of petroleum chemistry, must be free from sulfur compounds. To avoid these inconveniences, the present invention makes use of carbon monoxide which can be easily removed from the fraction and has the ability to selectively inhibit the activity of the catalysts. This selectivity is often superior to that produced by sulfur compounds.

It is known that carbon monoixide constitutes a catalyst poison and its presence was, therefore, avoided in most of the prior art hydrogenation processes.

It has now been discovered that carbon monoxide has a selective and therefore favorable action in the poisoning of the metallic catalysts that are used in the hydrogenation of diolefins, provided this agent is used in well defined proportions. This surprising observation is the basis of the present invention.

It has been found that the carbon monoxide content necessary to obtain good selectivity in the action of the catalyst can be very small. It is preferably between and 1000 p.p.m. by volume, relative to the hydrogen. Higher proportions are not advantageous because they deactivate the catalyst to the extent that it is not possible 4 EXAMPLE 1 thereafter to sufiiciently hydrogenate the gum-producing Temperature 100 to 120 C. hydrocarbons. Conversely, amounts smaller than 10 Pressure 40 atm. .m. do not confer sufficient selectivity to the catalyst. Spatial rate (vol./vol./hour) =2. An optimum proportion is about 50 to 600 p.p.m. It is Molar ratio H /liquid charge=2.5.

Products (molar percent) I II III Alter treat- Alter treat- Aiter treatment in the ment in the Charge ment in the presence 0! presence of (molar absence or sulfur carbon Compound percent) sultur (thlophene) monoxide Benzene 90 90 Cyclohexaue 0 00 0 Isoprene 10 0 0. 10 0. 10 Sum of the isopentenes 0 0 9. 60 9. 89 Isopentaue 0 10 0. 24 0. 01

also here to be mentioned that carbon monoxide is, of course, inexpensive, and easily produced.

The catalyst can be dispersed in the charge or disposed in a layer which may be stationary, mobile, or fluid. In particular embodiments, it is composed of metallic nickel or cobalt, or it is mixed with other catalytic constituents, as, for example, compounds of Group VI metals, especially of molybdenum. Inert nonacidic supporting materials are also useful, for example, alumina, silica, or magnesia.

In cases where a support is used, the nickel and/or cobalt is advantageously present in amounts of about 2 to 50% by weight of the catalyst.

The catalyst of the present invention can be prepared by known methods, as disclosed, for example, in the books Chemistry of Petroleum Hydrocarbons, vol. 3, and Catalysis, v01. 3.

In carrying out the present process, it is preferable to have at least one portion of the charge remain in the liquid phase. For this purpose the total pressure is kept sufliciently high, at least equal in most cases to 10 atm., and preferably between 30 and 80 atm. The spatial rate (volume of the liquid charge/volume of the catalyst/ hour) is between 0.5 and 10, and preferably between 1 and 4. The rate of gaseous hydrogen relative to the rate of the liquid charge is, for example, between 50 and 500 liters/liter, but variation beyond these last two values is to be understood as within the operational variables of the process.

The reaction temperature is between 50 and 250 C., preferably between about 120 and 180 C.

The hydrogen is used in the pure state or is diluted by an inert gas, especially by saturated lower hydrocarbons. The presence of sulfur compounds in the hydrogen gas is to be avoided since there should be less than 50 p.p.m., and preferably less than 5 p.p.m. of sulfur by weight in this gas.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative and not limitative of the remainder of the specification and claims in any way whatsoever.

In the first run as indicated in column I, the liquid charge and the hydrogen do not contain an inhibitor compound. In the second run as indicated in column II, the liquid charge contains 300 p.p.m. by weight of sulfur in the form of thiophene (the hydrogen is pure), and in the third run as indicated in column III, the charge does not contain any sulfur but the hydrogen contains 300 p.p.m. by volume of carbon monoxide. The products indicate that nickel in the absence of inhibitor does not have good selectively because on the one hand it permits the complete hydrogenation of the intermediate olefins, and on the other hand a large portion of the benzene is also hydrogenated. On the contrary, the addition of inhibitor compounds makes it possible to obtain a selectivity resulting in a minimum formation of saturated hydrocarbons (isopentane). It is found that carbon monoxide confers a selectivity that is definitely superior to that of thiophene.

EXAMPLE 2 The process is performed on a steam cracking fraction whose composition and characteirstics are as follows:

Chemical composition, percent by volume:

The catalyst is the same as the previous example. The proportion of carbon monoxide in the hydrogen is 600 p.p.m. (by volume).

The results are given in the following table:

The gums are measured directly on the crude fraction at the outlet of the reactor and not after distillation.

The various measurements indicated are made according to the A.S.T.M. standards. The maleic anhydride index is measured according to U.O.P. standard method 326.58. A very stable product, as indicated by a very high period of induction, is obtained, with only a very small loss of clear octane index. The antioxidant is N,N-di-sec.- butyl-paraphenylene-diamine.

EXAMPLE 3 The process of Example 2 is repeated at a temperature of 140 C., with different ratios of carbon monoxide to hydrogen.

The results obtained are presented in the following table:

In the above specification, the following ASTM methods have been used:

Analysis: Number of ASTM method Sulfur D-1266 Bromine index D-1159-61 Gums present D-381-61T Potential gums D-87 3 Period of induction D-525-55 Octane number D-908-5 8 Density D-941-55 Distillation D-86-62 Whereas in the above examples carbon monoxide was admixed with hydrogen before being contacted with the catalyst and the charge, it must be pointed out that equivalent results are obtained when said carbon monoxide, is admixed with the charge and the resulting mixture is thereafter contacted with the catalyst and hydrogen.

The preceding examples can be repeated with similar success by substituting the generically and specifically described reactants and operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. Consequently, such changes and modifications are prop- Product 200 ppm. 600 ppm. 7,300 .m. Analysis Charge No C0 CO 00 p GO Malelc anhydride index (MAV) 74 0 1. 5 4 18. 5 Bromine index (IBr) 66 0 49. 5 53 56 Gums present (atter wa mg./100 cm. 7 6 6 7 8 Potential gums in mg./100 cm.*.. 7, 400 0 150 250 1, 500 Period of induction in minutes with 10 p.p.m.

of antioxidant 60 960 960 800 250 Octane number clear 98 91 97 97 97 Octane number T.E.L. (0.05%) 101 97 101 101 101 This table shows that in the absence of CO, the hydrogenation of the diolefinic and olefinic double bonds is complete (MAV-=0, IBr=0). This, results in a prohibitive lowering of the octane number wherein the industrial tolerance for this type of treatment is a single point for the variation of the clear octane number. On the contrary, with too large a proportion of carbon monoxide, the resulting fraction does not have the required stability, the induction period, for example, being much too small, i.e., 360 minutes being the minimum permissible limit. The proportion of potential gums is also much too high.

EXAMPLE 4 The process of Example 3 is repeated at the temperature of about 105 C. It is found that in this case the tolerance in carbon monoxide is still less, the minimum tolerable limit for the induction period being reached at about 1000 p.p.m. of carbon monoxide in the hydrogen.

EXAMPLE 5 The process of Example 2 is repeated with a cobalt catalyst substituted for the nickel catalyst. The results are comparable with the results of Example 2.

EXAMPLE 6 The process of Example 2 is repeated, with a mixed cobalt/nickel catalyst substituted for the nickel catalyst. The results are comparable with the results obtained in Example 2.

erly, equitably, and intended to be, within the full range of equivalence of the following claims.

What is claimed is:

1. In a process for selectively hydrogenating a mixture of hydrocarbons having less than about 50 parts per million by weight of sulfur and containing diolefinic or alkenyl aromatic compounds, comprising contacting said hydrocarbons with hydrogen in the presence of hydrogenation catalyst comprising a metal selected from the group consisting of nickel and cobalt at a temperature between about 50 and 250 C., the improvement comprising the incorporation of carbon monoxide in the proportion of about 10 to 1000 parts per million by volume of said hydrogen.

2. The process of claim 1 wherein at least a portion of said hydrocarbons is in the liquid phase under the reaction conditions.

3. The process of claim 2 wherein said hydrocarbons have a boiling point between about 20 and 220 C.

4. The process of claim 1 wherein said proportion of carbon monoxide is between about 50 and 600 parts per million by volume of said hydrogen.

5. The process of claim 1 wherein the hydrogenation is conducted at a pressure between about 30 and atmospheres.

6. The process of claim 1 wherein said hydrogenation temperature is between about and C.

7. The process of claim 1 wherein said metallic cata- 7 8 iyst is deposited on a support in an amount of about References Cited 2m 50% by Weight UNITED STATES PATENTS 8. The process of claim 1 wherein said hydrogenatlon 2 397 105 4/1943 Klein 260 677 catalystlsmckel' 3,116,233 12/1963 Douwes et a1. 208-143 9. The process of claim 1 whereln said hydrogenanon 5 3,330 758 7/1967 Simpson 208 17 catalyst whalt- 3,308,071 3/1967 White 252-457 10. A process as defined by claim 1 wherein said hydrogenation catalyst further comprises a compound of DELBERT E. GANTZ, Primary Examiner a Group VI metal. I t

11. A process as defined by claim 1 wherein said hy- 10 NELSON Asslstan Exammer drogenation catalyst further comprises a compound of US. Cl. X.R.

molybdenum. 208-143 

